Blasting apparatus



Sept. 25, 1962 Filed June 26, 1959 C. W. EILO ET AL BLASTING APPARATUS 4 Sheets-Sheet 1 FIG. l

CLYDE W.EILO JOHN W, OTT INVENTORS AGENT Sept. 25, 1962 c. w. ElLo ETAL 3,055,299 BLASTING APPARATUS Filed June 26, 1959 4 Sheets-Sheet 2 FIG. 2 FIG 3 i I I6 @"w Y lla FIG. 9

C LYDE W. El LO JOH N W. OTT INVENTORS AGENT sept. 25, 1962 c W. Emo Em 3,055,299

BLASTING APPARATUS Filed June 26, 1959 4 Sheets-Sheet 3 FIG. 7

CLYDE W. EiLO JOHN W. OTT INVENTORS BY MQPM AGENT S999- 25, 1962 C. w. EIL@ Em 3,055,299

BLASTING APPARATUS Filed June 26, 1959 4 Sheets-Sheet 4 FIG CLY DE W. El LO JOHN W. OTT INVENTORS BY Sven/ex AGENT Unite 3,055,299 BLASTHNG APPARATUS Clyde W. Eilo, Succasunna, NJ., and .lohn W. Ott, Wilmington, Del., assignors to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Filed .lune 26, 1959, Ser. No. 823,162 9 Claims., (Cl. 102-25) This invention relates to a blasting device of the reutilizable type which employs a thermally decomposable gasproducing charge capable of self-sustained decomposition, and a rupturable closure element as a pressure release means, and to ring head structure associated with the said device for quickly loading and tiring same. In another aspect this invention relates to a packaged blasting material, as a cartridge, in combination with a device of the above-described type, which package contains a rupturable member as an integral part thereof, and to seating means associated with the device for facilitating accurate seating of the said rupture member to facilitate quick loading of the charge. In still another aspect the invention relates to structure associated with the above-described seating means for release of gas pressure built up in the chamber but which, due to failure of the system, cannot be released in the normal manner. In another aspect this invention relates to a blasting device of the above type containing a removable chamber end closure, as a tiring head, and structure associated with the said end closure for slidably inserting and rotatably locking same into closing position and for supporting and seating the said cartridge as part of the closure unit during said insertion and locking o-f same, and then biasing the cartridge in seated position upon completion of the closure.

Blasting apparatus of the reutilizable type which ernploys a gas-generating charge as the energy source is Well knofwn in the art. Such a device contains a thermally decomposable charge capable of self-sustained decomposition responsive to initiation by local heating, generally by electrically -actuated means, and contains a rupturable closure member positioned to coniine the resulting gas decomposition product up to a predetermined pressure and to then rupture to release the high pressure gas to the area to be blasted. One such well-known device is that of the Hydrox type and is particularly adapted to the mining of coal in view of the comparatively gentle heaving action that results from the blast and in View of the high safety factor that Warrants its use in gassy and dusty mines. Various compositions of gas-generating charges have been employed among which are equimolar mixtures of sodium nitrite and ammonium chloride, ammonium nitrate-sodium nitrate mixtures and the like, as further exemplified herein.

Assemblies of the above-described type have utilized various forms of chamber closure members, rupture means and `charge assemblies dependent upon the specific problem at hand. Thus, the end closure which generally serves as a firing head, i.e., to convey electric current for electrically actuating initiation `of the charge, has generally been allixed to the chamber by various means involving a threaded connection in some form. In any event, removal of the firing head from the chamber for reloading has been unduly time consuming which has consequently impaired the lrate of reloading with resulting low frequency of shots.

Another problem in connection with the above type blasting device has been in the replacement of the rupture disk, Which in many instances, has involved disassembly of the device or if the rupturable member is part of the cartridge, there has been quite some problem involved in taking the necessary precautions to be certain that the rupturable element is properly seated so as to completely confine the gases up to the predetermined pressure level for release. Still another problem has been presented in numerous instances by the failure lof the rupture element to disintegrate sufficiently for its discharge from the device with the high pressure gases as result of which the insuli'lciently disintegrated particles block passage of the gases to preclude venting and thereby prevent further use of the device until the pressure is relieved.

This invention is concerned with a blasting device of the above type which provides a firing head-cartridge assembly together with associated seating means for the rupturable element which can be more quickly loaded than heretofore and which is, accordingly, capable of a higher frequency of shots and thus higher yields of breakage over a given operating period. The device also provides for venting of gases from the chamber when for any reason the venting fails due to failure of the rupturable member to disintegrate to a suicient degree.

In accordance with the invention apparatus adapted to load and employ a gas-generating charge of the type above described, at a rate higher than heretofore, and which provides for venting of the high pressure gases generated and accumulated when normal venting means fails, is provided, which comprises an elongated chamber; a conduit with at least one port in a side wall thereof, as a ported venting means, disposed at one end of said chamber in direct gastight communication with the interior thereof; a closure head for said chamber in slidably closing engagement with the end thereof farthest from said venting means and adapted to be locked in said slidable and closing engagement; a partition Within said chamber closing same transversely to the longitudinal chamber axis; said partition containing a passageway therethrough substantially coaxial with the said chamber; the Walls of said partition and said passageway, intersecting adjacent said chamber at an angle preferably not exceeding about whereby to form Va cutting, or shearing, edge along the line of said intersection as a seat described hereinafter; a closed elongated package formed from a combustible material and containing a charge of a thermally decomposable gas-producing composition capable of self-sustained decomposition in response to local heating; a closure member for said package, at one end thereof, having a rounded surface external to said package adapted to t against said formed cutting edge and to then rupture in response to development of predetermined gas pressure by decomposition o-f said charge, and said package being axially disposed in said chamber with the said closure therefor in position for said seating; biasing means, within said chamber, secured to said closure head and extending into contact with said package to bias same in said seated position; electrically actuated heating means Within said chamber for initiating sa-id charge; and means for conducting electric current through said closure head to said initiating means t0 actuate same.

The tiring head, or chamber end closure, comprises, in a preferred form, a breech block, generally an electric conductor, as a closure for one end of the chamber with electric lead Wires extending from outside said chamber into said block, and a pair of electrodes extending into said chamber, fro-m the block, and operatively connected with the leads to receive elecrtic current therefrom for initiation of the gas-producing charge. Each of a plurality of lugs extends from the side of the block and is adapted to engage, and ride in, a groove in a side Wall of the chamber end during insertion of the block in the chamber end to clo-se the chamber. The lugs are in alignment with a passageway in the chamber Wall adjacent each groove, when the block is fully inserted in the chamber end. Thus by rotating the block, the said lugs are caused to engage the passageway and lock the block in position as a closure for the chamber. A further feature of the breech block, or ring head, above described, is a pair of conduits which extend from the chamber interior through a portion of the block toward the chamber wall and are adapted to engage conduits extending through the charnber wall when the block is only partially disengaged from its locking position. This feature provides for venting gases from the chamber, developed by decomposition of the charge, when for any reason their normal discharge from the chamber is blocked.

The cartridge assembly comprises the gas-producing charge disposed in a closed elongated package formed from a combustible material and contains a rupturable element as an end closure, i.e., as an integral part thereof. The package is supported Within the chamber so as to seat the rupturable member against the annular cutting edge, the rupturable element together with the wall which contains the cutting edge transversely closing the chamber. The rupturable element seated against the cutting edge bursts or disintegrates in response to development of the predetermined gas pressure above referred to. The package, by support of same as part of a unit with the ring head, is adapted to be charged with the firing head. Biasing means secured to the firing head and extending longitudinally into the chamber but short of the entire length of the cartridge support means is provided and is adapted to bias the cartridge into seated position when the tiring head is completely inserted. The cartridge support means secured to the tiring head is preferably a tray or shelf disposed substantially perpendicularly to the face of the head and extending a sufficient distance to support the cartridge.

The rupture member is preferably of spherical contour along its surface external to the package to simplify the problem of making a pressure-tight contact with the seat upon complete insertion of the firing head-cartridge into the chamber. Although the spherical external surface is preferred, a generally rounded contour can be advantageously employed. In this manner there is provided a maximum of tolerance, i.e., variance of the elongated package from a substantially coaxial position in the chamber, whereas the greater the variation in the spherical contour, the more rigid is the requirement that the cartridge be centered substantially coaxially with the annular cutting edge.

Occasionally, in this type of device the rupturable element, although it breaks, fails to disintegrate suiciently to be removed from the device and the resulting pieces block the exitway to prevent venting of the built up gases and thereby present a problem of disassembly for reloading. Accordingly, the invention provides for grooves longitudinally and/or spirally disposed along the wall of the exitway for conveying gas flow along, and within the inner surface of, the tube wall even though the tubular portion is blocked.

The invention is illustrated with reference to FIGURES 1-11 of the drawings of Which FIGURE 1 is a front elevational view in cross section of a blasting device of the invention containing one embodiment of the firing headcartridge assembly including cartridge support and biasing means together with seating structure therefor, and means associated with the seating structure for venting gases built up in the system when the normal discharge means fails; FIGURE 2 is a sectional view of the block element of the breech, or closure, member of FIGURE 1; FIGURE 3 is an enlarged cross sectional View of an insulated conductor-connector of FIGURE 1 for connecting a lead Wire with an electrode in the chamber; FIGURE 4 is illustrative of a seating of a rupturable element of, and alternative to that of, FIGURE 1; FIGURE 4a is illustrative of a preferred block assembly slidably removable from the system and containing seating means for the rupturable element; FIGURES 5, 6 and 7 are plan views further illustrative of the breech block closure member which is slidably engageable with the chamber and can be locked in complete closing relation therewith While at the same time supports the cartridge until closure is complete and upon completion of the closure, biases the cartridge in operating position; FIGURE 8 is an end view of the chamber of FIGURE 1 adapted to accept a breech block closure of FIGURES 1 and 5-7; FIGURE 9 is a view taken along the line 9 9 of FIGURE 8 illustrative of grooves in the side wall of the chamber for accepting lug elements of the breech blo-ck closure of FIGURES 1 and 5-7; FIGURE l() illustrates the invention as applied to a conventional blasting device of the reutilizable type wherein gas is generated at high pressure and discharged via ported vents to the borehole; and FIGURE l1 illustrates the invention as applied to a chamber-drill assembly wherein the gas is generated at high pressure and is discharged through a rotating drill stem and the stem wall to the borehole without need for withdrawal of the drill from the borehole.

With reference to FIG. l, elongated housing 10, generally cylindrical, is open at each end and contains partition, or Wall, 11 disposed across its longitudinal axis to close housing 10 to form chamber 13. Conduit 11a is disposed through Wall 11 and is preferably coaxial with chamber 13.

The open end of chamber 13 opposite wall 11 is closed by firing head assembly 12 containing lead wires 13a and 13b insulated from each other and extending into head section 12a and in electrical conductive contact with electrodes 9a and 9b, respectively. Cartridge 16 is elongated and is closed at its end closest to head assembly 12 by any 1suitable means and at the other end by a rupturable element 16a and contains a main charge, disposed so as t0 be adjacent rupturable closure member 16a, of (1) a solid composition 17 capable of thermal decomposition with the evolution of gases without llame and capable of self-sustained decomposition when initiated by heat applied merely to a local portion thereof, (2) a suitable primer composition 1S intermediate the end of cartridge 16, opposite closure 16a, and charge 17, and (3) an electric initiator 19 embedded in primer 18, the primer 18 and initiator 19 being in operative relationship to initiate decomposition of charge 17 -in response to heating by passage of electric tiring current across electrodes 9a and 9b through leads 21a, 2lb and initiator 19. Other suitable primers and initiators can be employed in place of those herein illustrated, as later described.

Cartridge 16 is disposed within chamber 13 so as to seat closure 16a against the face of conduit 11a adjacent thereto and is initially biased in that seated position by any suitable biasing means such as coil spring 22 supported against closure member 12.

Conductor closure block, or ring head, 12, which closes chamber 13 and contains leads 13a and 13b and electrodes 9a and 9b, comprises electrical conductor block 12a containing recess 15 in its end external to chamber 13 and closure nipple 20 threadably secured across the open end of recess 15. Insulated electrical leads 13a and 13b extend from outside assembly 12, supportably through nipple 20, into and through recess 15, and into central block portion 12a. Lead 13a is terminated in block portion 12a in electrical conductor block 47, the latter insulated, in recess 8, sce FIGURES 2 and 3, from block 12a by a surrounding insulating layer 47a. Any suitable support for lead 13a in block 47 can be utilized. Now preferred is a friction support prepared by insertion of the end of lead 13a, without removal of insulation therefrom, into an opening, or recess, 48 in block 47, in a manner to provide scraping of insulation from the lead wire and an accumulation of displaced insulation in binding relationship with the block Wall forming opening 48 to thereby secure lead 13a in insulated electrically conductive contact with block 47. Lead 13b is supported in recess 7 in block portion 12a, see FIGURE 2, in direct electrical Contact therewith by any suitable means such as by a friction support of the type above described with reference to lead 13a in block 47.

Electrode 9a within chamber 13 is extended into and through recess 49 of block portion 12a, see FIGURE 2, toward and into recess 51 of conductor block 47, see FIGURE 3, in threaded electrically conductive engagement therewith. Electrode 9a is insulated in recess 49 from block portion 12a by any suitable means such as a nonconductive packing t?. Electrode 9b is threadably engaged with the block portion 12a in recess 52 so aS to be in direct electrical contact therewith.

Elongated cartridge guide, or shelf, 25 in chamber 13 is secured at one end in the recess portion 25a in the end of block portion 12a so as to extend in a direction substantially parallel with the axis of chamber 13. Guide 25 serves as a carrier for cartridge 16 during insertion of same into chamber 13 as described more fully hereinafter.

It is important when supporting cartridge 16 in chamber 13 that rupturable end member 16a be seated against a suitably sharp edge to secure seatings during operation with successive charges with minimum variation in the rupture pressures required. As shown, closure member 16a is seated against the end, or face, 53 of recess 54 in wall 11 adjacent chamber 13, preferably coaxially with conduit 11a, and having a diameter larger than that of conduit 11a. The face 53 is preferably in a plane perpendicular to the axis of chamber 13, and the inner Wall of recess 54 adjacent face 53 is preferably in a plane parallel to the said chamber axis, under which conditions a suitably Sharp seating edge is provided. If desired, that angle formed by the intersection 0f the two surfaces, i.e., face 53 with the inner wall of recess 54, encompassing a portion of wall 11, can be less than 90 although 90 is generally sufcient. Inasmuch as the contour 56 of the end wall of chamber 13 is generally conical rather than at due to preferred fabrication procedures utilized, it is advantageous to provide recess 57 in wall 11 intermediate recess 54 and the interior of chamber 13. Recess 57 is preferably coaxial lwith recess 54, having a diameter larger than that of recess S4, and containing a hat contour 58 common to the face 53. In this manner the rupturable element 16a is seated against a suitably sharp edge, Whereas without recess 57 intersection of the conical contour 56 with end 53, or of conduit 11a, would form an angle greater than the above described 90 with a concomitantly duller seating edge.

With reference to FIGURE 4 is shown a suitable seating for the element 16a without the need for a supplemental recess 57 in which the contour 56a at the end of chamber 13 is dat and lies in a plane perpendicular to the axis of the chamber 13 to provide, with the inner Wall of recess 54, for the desired sharp seating edge. If desired, conduit 11a can be extended into chamber 13 in lieu of recess 54 to provide its own end or face as a seat for member 16a, in which event the contour of the end wall of chamber 13 is preferably hat, as illustrated with reference to contour 56a of FIGURE 4.

Recess 54 is provided along its inner wall Iwith spirally disposed threads 59 which provide for release of gas from chamber 13 in the event that rupture of element 16a is incomplete so as to otherwise cause stoppage of recess 54 to block the escape of gases from chamber 13 into and through conduit 11a.

Conduit 11a contains longitudinally extending slots 61 in its inner wall in an area adjacent recess 54 to further provide for escape of gases from chamber 13 in the event of stoppage of conduit 11a due to incomplete breakup of the rupturable element 16a.

A now preferred embodiment of structure for forming a seating means 53 and an inlet portion of conduit 11a including, when desired, elements 59 and 61 for facilitating gas pressure release when the rupturable element 16a fails to disintegrate suiciently, is shown in FIGURE 4a. Thus, a block 53a preferably cylindrical, containing a bore 11a and a seating face 53 together with threads 59 and grooves 61 is slidably disposed in partition 11, coaXially with conduit 11a and chamber 13 and is maintained in gas tight relation with partition 11 by O-ring 53h intermediate the external Wall of block 53a and the adjacent surface of partition 11 containing block 53a. Block 53a can be slidably moved into, and from, operating position in partition 11 for quick inspection, and/or repair or replacement of cutting face 53 as may be rcquired. Block 53a is inserted in, and withdrawn from, operating position via the open chamber end (opposite partition 11) and chamber 13. Although the slidable engagement of block 53a is preferred, any means for engaging block 53a in partition 11 can be utilized such as by threads.

Firing assembly 12 is quickly engageable into, and disengageable from, operating position. Thus, block 12a contains spaced apart lugs 72 along the periphery of a central or lower portion thereof. The open end section of shell 10 contains grooves 73, see also FIGURE 8, substantially parallel with the axis of chamber 13, each in alignment with a lug 72 of assembly 12 when the latter is inserted into the open end of chamber 13. As shown in FIGURE 9, each groove 73 is of length at least sufcient to terminate adjacent a circumferentially disposed passageway, or undercut, 74 in the wall of chamber 13 and in open communication with each groove 73. Passageway 74, see FIGURES 5-7, 8 and 9, is preferably positioned immediately below grooves 73 so as to receive the lugs 72 from the groove 73 when the ring head 12 is fully inserted into the end of the chamber 13 and rotated as described hereinafter. Block 12a is advantageously tapered along an end section 12a in which ca-se the inner wall of chamber 13 is tapered so as to seat the tapered end 12a. O-ring 12b around tapered end 12a' lforms a gas-tight seal lbetween block 12a and the wall of chamber 13 when the head assembly 12 is fully inserted as a closure for chamber 13. In Athe seated position with lugs 72 at the foot of grooves 73 and Within passageway 74, head assembly 12 is adapted to Ibe rotated so as to move lugs 72 along the circumferentially disposed passageway 74. In this manner .the lugs 72 are adapted to be disposed in an undercut portion of block 12a, i.e., beneath the chamber wall por-tion above passageway 74, in locked position as a closure for chamber 13.

As illustrated with reference to FIGURES 5, 6 and 7, firing head assembly 12 is inserted into chamber 1 3 with each lug 72 engaged with a groove 73 in the chamber wall. Thus, as shown in FIGURE 5, firing head assembly 12 is inserted into chamber 13 and is disposed so that the entire portion of each lug 72 is directly aligned with .a groove 73 so that each lug can move within a groove 73. Assembly 12 in this position is referred to herein as unlocked within chamber 13. As illustrated with reference to FIGURE 6, assembly 12, when in the unlocked position of FIGURE 5 and then rotated either clockwise or counterclockwise, will cause each lug 72 to move into an adjacent portion of passageway 74, intermediate a pair of grooves 73, so that each lug 72 is locked in position, i.e., so far as longitudinal movement out of chamber 13 is concerned, by that portion of chamber wall 13 which forms a top wall of passageway 74 and protrudes over each lug 72 to prevent its upward movement. To unlock assembly 12 in chamber 13 it is necessary only to rotate the assembly 12 from its position of FIGURE 6 either clockwise or counterclockwise sufficiently to dispose each lug 72 in direct alignment with a groove 73, as shown in FIGURE 5.

A system of conduits, illustrated with reference to FIG- URES l, 5, 6 and 7, is provided for venting high pressure gas from chamber 13 in those instances wherein for any reason discharge of gas via conduit 11a has failed. These conduits are so disposed as to provide for venting lthe said gas by rotating the firing assembly 12 of FIGURE 6 toward the unlocked position of FIGURE 5 but short of the latter position so as to engage the said conduits and provide for discharge of gas from the cham-ber through a portion of the firing block and the chamber side wall 7 without disengagement of the ring head from the chamber.

Thus, as illustrated in each of FIGURES 5, 6 and 7, a plurality of conduit pairs 76 and 77 is disposed through the chamber wall from the outside of the chamber toward the head 12a so as to be closed by assembly 12a When the latter is fully inserted in position in chamber 13, i.e., except for conduits 78 and 79 described hereinafter. Conduits 78 and 79 extend through a portion of assembly 12 from its face adjacent the chamber 13 interior, toward the wall of chamber 13. When assembly `121/1 is in completely locked position as shown with reference to FIGURE 6, conduits 78 and 79 are out `of direct communication with conduits 76 and 77. Each conduit pair 76 and 77 extends into chamber 13 along any suitable path preferably so as to terminate in a portion of the inner wall of chamber 13 directly below a groove 73 as illustrated with reference to FIGURE l. Each conduit pair 78 and 79 is advantageously extended from direct communication with the chamber 13 interior face in a direction substantially parallel to the axis of chamber 13 and then at an angle toward the chamber 13 wall, i.e., as an L, so as to be in direct communication with conduits 76 and 77, respectively, when the assembly 12 is in the unlocked position of FIGURE 5. Although it is not important per se that conduits 76 and 77 directly communicate with conduits 78 and 79, respectively, in the said unlocked position, that arrangement does conveniently provide for the out-of-contact relationship of the conduit pairs 76-77 and 78-79 when assembly 12 is completely locked, see FIGURE 6, and for direct communication of one of the pairs of conduits 76 and 77 with one of the pairs of 78 and 79 when the block 12 is rotated from the locked position of FIGURE 6 to a partially unlocked position of FIGURE 7, it being understood that the direction of rotation is immaterial.

As illustrated with reference to FIGURE 7, when the locked firing assembly 12 of FIGURE 6 is rotated counterclockwise toward the unlocked position of FIGURE 5, lug 72 upon being moved partially into an adjacent groove 73a also moves conduit 78 in direct open communication with conduit 77a to provide for any required venting of chamber 13. Had block 12 been rotated in the opposite direction, i.e., clockwise, lug 72 would have been moved partially into groove 73b suiiiciently to directly communicate conduit 79 with conduit 76b so as again to provide for the Venting without moving the block entirely into the locked position of FIGURE 2.

In the operation of the assembly of FIGURE 1, ring head assembly 12, including guide shelf 25, is loaded outside chamber 13 with cartridge 16 and inserted into chamber 13 with lugs 72 in place in a corresponding groove 73 (FIGURE 9) in the chamber side wall. Care is taken lthat upon insertion of assembly 12 and cartridge 16 into place in chamber 13, the rupturable closure member 16a is uniformly urged against its seat at face 53 under some tension from biasing means 22 but short of complete seating. The assembly 12 is then urged forward to apply full biasing tension to cartridge 16 and to engage lugs 72 into final position and alignment with passageway 74 (FIGURE 9), at which time seating is completed and head 12 is rotated suiciently to lock each lug 72 under a chamber wall section above passageway 74, as more specifically illustrated with reference to FIG- URES 5, 6 and 7. Rotation of assembly 12 about 20-25 is generally suiicient depending upon the number and distribution of lugs 72 and grooves 73 and their spacing. When the tiring head and cartridge assembly is in the thus loaded and locked position, spring 22 biases cartridge 16 into operating position and shelf 25 serves no further function.

FIGURE shows a cartridge-firing head assembly of the invention as an element of a blasting device of the reutilizable type. Thus, with reference to FIGURE l0, the assembly of charge-tiring head and associated structure, of FIGURE 1 is shown in skeleton form as unit 80 and is connected at its end opposite that containing tiring head 12 in gas-tight relationship with a venting head 81, as by threaded engagement `82. Venting head 81 is tubular with an open end 83 abutting conduit 11a extending through wall 11 of housing 10. Venting head 81 is closed at its opposite end 84 and contains at least one port 86 in the side wall. Venting head 81 threadably attached by thread means 82 to housing 16` is secured in gas-tight relationship with housing 10 by O-ring 87 adjacent threads 82 in recess 88 in the end of housing 10.

In the operation of the embodiment of FIGURE l0 the assembly is supported against the face of the formation to be blasted with the venting head 81 disposed within a borehole. The assembly Si) is loaded as described with ref erence to FIGURE l. The loading procedure completed, leads 13a and 13b are connected with a suitable power source so as to be ready for tiring. Upon firing, element 19, such as an electric squib, is initiated and in turn initiates ignition of primer 1, such as a smokeless powder, and the latter, by transfer of heat of combustion to the main charge 17, initiates self-sustained decomposition of charge 17. Responsive to generation of gas product up to a predetermined elevated pressure value, element 16a ruptures and gas at high pressure is released Via conduit 11a into vent head -81 in out-ports 86 to the wall of the borehole to provide the desired breaking effect.

With reference to FIGURE 1l an assembly of firing head-cartridge and associated structure of FIGURE 1 is shown as an element of a combined tiring chamber and drill structure for simultaneously drilling a formation and tiring Without the need for withdrawing the drill stem lfrom the borehole as disclosed and claimed in the copending application of Robert W. Lawrence and Robert J. Shiel, Serial No. 783,867, filed December 30, 1958. Thus, with reference to FIGURE 1l, the charge-firing head and associated structure of FIGURE 1 is shown in skeleton form as unit and is connected at its end opposite tiring head 12 with a rotatable drill stem 24 with port holes 37 in its side wall for receiving high pressure gas from chamber 13 and delivery of same to the wall of the borehole without the need for withdrawing the drill from the borehole. Thus, drill assembly 23 comprises a drill stem 24, a bit 26 secured to one end of stem 24 and a perforation 27 longitudinally, preferably coaxially, extending from the end of stem 24 opposite bit 26, and toward bit 26, for at least a major portion of the length of the stem to form a hollow stem.

Drill assembly 23 at its open end, i.e., opposite bit 26, is rotatably mounted in elongated housing 10 so as to dispose perforate section 27 in direct communication with interior of conduit (11a. The stem section 24 with end portion 24a, of smaller diameter, is operatively secured to housing 10 in recess 28 of housing 10, preferably c0- axially with conduit 11a, by suitable sleeve bearing, retainer ring, and O-ring means so as to maintain gas-tight relationship of the inner wall of recess 28 with stem 24 and thereby maintain perforation 27 in direct open gastight communication with conduit 11a. Flights 34 are spirally disposed around the portion of stem 24 insertable in the formation to be drilled so as to direct cuttings along stem 24 away from the bit. Ports 37 are disposed in the side wall of stem section 24 preferably in close proximity to bit 26, the total cross sectional diameter of ports 37 being at least equal to that of conduit 11a. Means for rotating the entire stem assembly 24 to operate bit 26 comprises a conventional reducer assembly contained within housing 38 and driven by rotation of shaft 39 and operatively connected with drill stem 24 to rotatably drive it. Cone member 41 is supported along stem 24 adjacent gear assembly 38 and has a knurled external surface to facilitate grinding action of the cone against the face of the formation to seat the cone and form a closure for the borehole when stem member 24 and bit 26 are fully advanced into the formation. Cone member 41 can be spaced apart from housing 38, or abutted, as desired.

In the operation of the device of FIGURE 11, the entire assembly of FIGURE 11 is moved into drilling position by suitable moving means (not shown). Drill assembly 23 is driven at the required rotation rate by rotation of shaft 39, through the gear reduction assembly in housing 38, and the total assembly is moved forward during drilling. Upon completion of penetration, the charge, having been loaded as described with reference to FIGURE 1, i.e., either during or prior to drilling, is initiated by firing current via leads 13a and 13b. Responsive to a predetermined pressure build-up in chamber 13, member 16a ruptures and permits flow of high pressure gases through conduit 11a, perforation 27 and ports 37 to the walls of the borehole to provide the desired breakage. The blast takes place ywithout removal of the drill stem from the borehole and upon removal of the breakage, the assembly can be continuously moved forward and the loading and shooting cycle repeated.

As is well known in the art, a thermally decomposable gas-producing charge capable of sustaining its decomposition, to be utilized as a source of high pressure gas as energy for blasting purposes, is initiated by heat developed by combustion of a primer composition which is, in turn, initiated by a suitable igniter means such as a resistance wire, a hot spark, a suitable squib assembly, r the like. In most instances an electrically heated resistance wire in contact with a primer composition ignites the primer within a period in the order of about 3-5 seconds. After from 0.2-1 second burning of the primer, a pressure is built up in the order of say 1200 p.s.i.g. in the closed chamber, which facilitates initiation of decomposition of the gas-producing charge. The gas-producing charge requires generally one second or less for complete decomposition of same, during which time pressure is built up to a value in the order of from about 8-20,000 p.s.i. At a predetermined pressure value in that range the rupture disk or other means employed for confining the high gas pressure in the chamber is actuated to permit release of high pressure gas from the chamber. Thus, the total time from initiation of the primer to release of high pressure gas is in the order of less than l0 seconds.

Although any suitable igniter means can be employed, a squib-type cap, i.e., an electrical activator 19, is now preferred in view of the ease and simplicity of procedure by which it can be incorporated within the cartridge in operative relationship with the primer to initiate same, and particularly in view of the simplified electrical firing system that can be employed for its actuation. This (activator 19, FIG. l) contains a gasless heat generating charge in a bronze shell, the shell being heated to a dull red without bursting. It does not become sufficiently hot to ignite methane-air mixtures when fired directly in such mixtures. An exemplary squib is one which contains a 0.5 g. mixture of Pb3O4/MnB2, 60/ 40, as an ignition composition loaded into a copper shell. It is ignited by electrically generated heat of a fine resistance of bridge wire within the mixture. Another squib assembly advantageously employed contains 0.5 g. antimony/potassium permanganate, 45/55, as an ignition composition, which is initiated by a matehhead, the entire squib assembly being in a copper shell. A now preferred resistance element, employed in lieu of a squib, comprises such an element that forms a knife edge facing the cartridge and attached to the chamber closure member, e.g., across electrodes '9a and 9b of FIGS. l and 2 and spaced suiciently from the closure block so as to cut into the cartridge in direct contact with the primer when the block is in closing position in the chamber. This embodiment affords a quick assembly ofthe charge within the chamber and eliminates the need for any wires in the chamber and eliminates the need for time `otherwise required for engaging lead wires from the electric power source with an ignition 10 system in the chamber. A hot spark-type igniter can be advantageously employed particularly in conjunction with a supplementary ignition composition.

It is also within the scope of the invention to employ a separate ignition composition in the cartridge in operative relationship with a separate primer composition and the main gas-producing charge. In that event a resistance wire-type igniter is advantageously disposed in operative relation with the said ignition mixture to initiate it. Exemplary ignition or activator Compositions (weight basis) employed in such an embodiment are:

Antimony 45.0 Potassium permanganate 55.0

Pb304 60.0 M11132 40.0

Exemplary gas-producing charges employed in the practice of the invention are:

Ammonium nitrate 49.0 Magnesium nitrate hexahydrate 34.0 Carbonaceous (nut meal, pulp, starch) 17.0

Ammonium nitrate 75.0 Calcium carbonate 25.0

Ammonium nitrate 90.0 Starch 10.0

Ammonium nitrate 65.0 Calcium formate 34.9 Calcium stearate 0.1

Guanidine nitrate 30.0 Magnesium nitrate hexahydrate 60.0 Carbonaceous 10.0

Any suitable primer composition can be employed. EX- emplary primers are as follows:

Guanidine nitrate 59.5 Ammonium persulfate 33.0 Cuprous chloride 6.5 Bentonite 0.5 Castor oil 0.5

Nitrocellulose 79.5 Dibutyl phthalate 18.5 K2SO4 1.0 Diphenylamine 1.0

Urea 45.0 Sodium nitrite 45.0 Cuprous chloride 10.0

Nitrocellulose 2.0.0 Nitroglycerin 15.0 Nitroguanidine 5 1.0 Ethyl centralite 7.0 Cellulose acetate 7.0

Guanidine nitrate 61.5 Ammonium persulfate 35.0 Cuprous chloride 2.5 China clay 0.5 Castor oil 0.5

The above composition (D) is particularly preferred.

'Ihe material from which the cartridge shell (cartridge 16, FIGURE l) is fabricated is one which is substantially completely consumed during decomposition of the main charge, paper being now preferred. Other shell materials include suitable plastic or fibrous materials. The destruction is essentially a combustion supported by combined oxygen in the main charge.

As will be evident to those skilled in the art, various modifications can be made `or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

What we claim and desire to protect by Letters Patent is:

l. In a blasting device comprising a pressure resistant chamber; a thermally decomposable gas-producing charge,

Within said chamber, capable of self-sustained decomposition when locally heated; means for initiating said charge to effect said decomposition; venting means in direct gastight communication with the interior of said chamber for receiving product gas from decomposition of said charge and delivery of same to its utilization; a rupturable member; an annular cutting edge in said chamber for seating said rupturable member as a rst gas-tight closure for said chamber, intermediate said charge and said gas venting means, and said rupturable member being adapted to rupture, when seated, in response to force of gas decomposition product developed at a predetermined elevated pressure by decomposition of the said charge; and a second closure for said chamber spaced apart from said rst closure, the improvement comprising a closed elongated package formed from a combustible material, within said chamber, and containing said charge; said package being closed at one end by an end closure member having a rounded surface external to said package; said package being adapted to be disposed in said chamber to seat said rounded end closure on said cutting edge as the above said gas-tight rupturable chamber closure; a block member, slidably insertable in `one end of said chamber, as said second end closure of said chamber, and adapted to be locked into position, by rotation, when completely so inserted; a shelf member secured to said block closure so as to extend into said chamber and support said charge package as a unit with said slidable block closure during insertion of same into position as said closure; and biasing means secured to said block closure and extending into said chamber to bias said package to maintain the said rounded end closure thereof in seated position when said block is completely inserted.

2. In a blasting device comprising an elongated pressure resistant chamber; a thermally decomposable gasproducing charge, within said chamber, capable of selfsustained decomposition when locally heated; means for initiating said charge to effect said decomposition; venting means connected at one end of said chamber in direct gas-tight communication with the interior thereof for receiving product gas from decomposition of said charge and delivery of same to its utilization; a rupturable member seated in one end of said chamber, as a gas-tight closure therefor, intermediate said charge and said venting means and adapted to rupture responsive to force or gas decomposition product developed at a predetermined elevated pressure by decomposition of said charge; and closure means for the end of said chamber opposite that containing said seated rupturable member; the improvement comprising a closed elongated package within said chamber and containing `said charge; an end closure member for said package, and said package being disposed in said chamber to seat the said end closure thereof as the above said gas-tight rupturable chamber closure; a block closure as the above said closure means for that end of said chamber opposite said seated rupturable member; said chamber containing a plurality of grooves in its inner wall, adjacent said block closure, each extending substantially equidistant longitudinally and terminating within the extremities of the said block closure; an equal plurality of lug members on the outer wall of said block closure member, each disposed and adapted to slide in one of said grooves when said block closure is moved into said chamber end; said chamber inner wall also containing a peripherally extending groove in a portion thereof adjacent said longitudinally extending grooves `and in open communication therewith so as to receive each said lug from its respective longitudinally extending groove when said block closure member has been moved into said chamber end to completely close same followed by rotation of said block; a spring assembly secured to the face of said closure member Within said chamber and disposed to extend substantially coaxially with said chamber to said package and to bias said package in said seated position when said block closure is in said position for rotation; and a tray secured to the face of said chamber closure member, within said chamber, and disposed so as to extend substantially parallel to the chamber longitudinal axis but beyond said spring assembly so as to support said package only when said block is out of said position for being rotated.

3. In a blasting device comprising an elongated pressure resistant cham-ber; a thermally decomposable gasproducing charge, within said chamber, capable of selfsustained decomposition when locally heated; means for initiating said charge to effect said decomposition; venting means connected at one end of said chamber in direct gas-tight communication with the interior thereof for receiving product gas from decomposition of said charge and delivery of same to its utilization, a seated rupturable member seated in said chamber, as a gas-tight closure therefor, intermediate said charge and said venting means and adapted to rupture responsive to force of gas decomposition product developed at a predetermined elevated pressure by decomposition of said charge; and closure means for the end of said chamber opposite that containing said seated rupturable member, the improvement comprising a closed elongated package, within said chamber, containing said charge; an end closure member for said package having a rounded surface external to said package, and said package being disposed in said chamber to seat said rounded end closure as the above said gas-tight rupturable chamber closure; a block closure as the above said closure means for the end of said chamber opposite said seated rupturable member; a biasing means secured to said block closure and disposed in biasing relationship with said package to maintain the end closure thereof in seated position; seating means for said rupturable member comprising an annular cutting edge;

1? and a conduit extending from said cutting edge to said gas vent.

4. In a blasting device of claim 3, a conduit extending from said cutting edge to said gas venting means, and the inner wall of the said conduit containing a plurality of grooves extending longitudinally toward said venting means.

5. In a blasting device of claim 4, said longitudinally extending grooves extending toward said venting means in a portion of said inner wall spaced from said annular cutting edge, and a plurality of parallel grooves extending spirally along the said inner wall intermediate said cutting edge and the said inner wall portion containing said longitudinally extending grooves.

i6. A blasting apparatus comprising an elongated rigid pressure resistant tubular chamber; a tubular venting head member connected in gas-tight communication with the interior of said chamber at one end thereof, and at least one port in a side wall of said head member; a block member disposed in the other end of said chamber in `gas-tight relationship Iwith said chamber as a closure for said chamber; the inner wall of said chamber adjacent said block containing a plurality of grooves each extending substantially equidistant longitudinally from the last said chamber end and terminating within the extremities of said block closure; an equal plurality of lug members on the outer surface of said block each disposed and adapted to slide in one of said grooves when said block is moved into said chamber end to close same; the said inner wall of said chamber also containing a peripherally extending groove adjacent said longitudinally extending grooves and in open communication therewith so as to receive each said lug from its respective longitudinally extending groove when said block has been moved into said chamber end to completely close same and is then rotated; a partition in said chamber disposed transverse to the longitudinal chamber axis as a closure yand containing a passageway of circular cross section extending therethrough coaxially with said tube; the Wall of said partition closest to -said closure block lying in a plane intersecting the wall forming said passageway, at an angle therewith not exceeding about 90, whereby to form a cutting edge along the line of said intersection `as described hereinafter; the said passageway connecting said cutting edge and said venting head member and containing a plurality of grooves longitudinally extending 'along at least a portion thereof, and also a plurality of grooves spirally disposed along the said passageway walls intermediate said longitudinally extending grooves and said cutting edge; a closed paper tubular package longitudinally disposed within said chamber intermediate said cutting edge and said chamber closure block and containing a charge of a thermally decomposable gas-producing composition capable of self-sustained decomposition in response to local heating and an electrically actuated heating means in operative relation with said charge for locally heating said charge to initiate said decomposition; a closure member for said paper tube at the end thereof closest to said cutting edge `and having a concave surface external to said package adapted to seat on said cutting edge; a spring within said chamber as an integral part of said block closure and extending therefrom substantially coaxially with said chamber a distance suicient to bias said package to seat the end closure thereof against said cutting edge when said chamber block closure is in position for being rotated as above described; and a tray within said chamber as an integral part of said 'block and extending therefrom toward said cutting edge beyond said spring but terminating at a point short of said cutting edge when said chamber block closure is in position for being rotated as described; and means for conducting electric current through said chamber closure member to said electrically actuated initiating means in said paper package.

7. In blasting apparatus of claim 6, said tubular venting head member being rotatably supported coaxially with said chamber in said gas-tight communication, and means for rotating said head member when so supported.

8. Apparatus for blasting which comprises an elongated chamber; a conduit with at least one port in a side Wall thereof, as a ported venting means, connected at one end of said chamber in direct gas-tight communication with the interior thereof; a closure head for said chamber in slidably closing engagement with the end thereof farthest from said venting means, and adapted to be locked in said slidable and closing engagement; a partition within said chamber closing same transversely to the longitudinal chamber axis; said partition containing a cylindrical passageway therethrough substantially coaxially with the said chamber; the wall of said partition closest to said closure head lying in a plane passageway, intersecting the wall forming said passageway, at an angle not exceeding about whereby to form a cutting edge along the line of said intersection as a seat described hereinafter; a closed elongated package formed from a combustible material and containing a charge of a thermally decomposable gas-producing composition capable of self-sustained decomposition in response to local heating; a closure member for said package, at one end thereof, having a round surface external to said package adapted to seat against said cutting edge and to then rupture in response to development of predetermined gas pressure by decomposition of said charge, and said package being axially disposed in said chamber with the said closure therefor in position for said seating; biasing means, within said chamber, secured to said closure head and extending into contact with said package to` bias same in said seated position; electrically actuated heating means within said chamber for initiating said charge; and means for conducting electric current through said closure head to -said initiating means to actuate same.

9. In apparatus of claim 8, a cylindrical section slida- Ibly disposed within said partition adjacent said chamber so as to be removable from said partition through said chamber, and coaxial with said chamber, thereby containing said cutting edge.

References Cited in the le of this patent UNITED STATES PATENTS 2,661,693 Diels Dec. 8, 1953 2,720,169 Smith Oct. 11, 1955 2,752,849 Swed July 3, 1956 2,756,677 McCullough July 31, 1956 2,869,462 Davidson et al. Jan. 20, 1959 2,973,713 Bfurton Mar. 7, 1961 FOREIGN PATENTS 761,453 Great Britain Nov. 14, 1956 

